--- /dev/null
+# AltusMetrum
+
+This is the design that started it all! Bdale got frustrated with existing
+commercial altimeters and decided to build his own. This project was
+presented in talks at LCA, SCALE, OLS, and Debconf in 2008.
+
+Here are photos of the front and back sides of the version 0.1 prototype PCB,
+which was 100% auto-routed on 2 layers using the
+[gEDA](http://www.gpleda.org)
+schematic and pcb tools.
+
+<a href="hpim2581.jpg"> <img src="hpim2581-thumb.jpg"></a>
+<a href="hpim2582.jpg"> <img src="hpim2582-thumb.jpg"></a>
+
+## Features ##
+
+### User View ###
+
+* Recording altimeter for model rocketry
+* Supports dual deployment (can fire 2 ejection charges)
+* Primary operations based on pressure sensor
+* 3-axis accelerometer
+* Temperature sensor
+* 2 serial ports for attachment of GPS and RF link modules
+* USB for data recovery and post-flight power source
+* Flexible battery choices
+* Designed to fit 24mm airframe tube
+
+### Developer View ###
+
+* NXP LPC-2148 Processor (ARM7TDMI-S)
+ * 512k Flash memory, 32k RAM
+ * USB plus lots of analog, digital, and serial I/O
+* Microchip 24FC1025 CMOS serial EEPROM
+ * 128k x 8
+ * I2C interface
+* Various Sensors
+ * Freescale MP3H6115A pressure sensor
+ * Freescale MMA7260QT 3-axis accelerometer
+ * Microchip MCP9700A temperature sensor
+ * (Honeywell 2-axis magnetic sensor left out of v0.1)
+* Software Features
+ * Written mostly in C with some ARM assembler
+ * Runs from on-chip flash, uses on-chip RAM, stores flight data to
+ serial EEPROM chip
+ * USB serial emulation for "console" interface
+ * Uses GCC, newlib, FreeRTOS, LPCUSB
+ * Based on a demo package written for the Olimex LPC-P2148 eval board
+ by J C Wren
+* Licenses
+ * The hardware is licensed under the [TAPR](http://www.tapr.org) [Open Hardware License](http://www.tapr.org/ohl.html)
+ * The software is licensed [GPL version 2](http://www.gnu.org/licenses/old-licenses/gpl-2.0.html)
+
+## Problems ##
+
+In addition to the various "oopses" that were found and fixed during initial
+turn-on of this board, several issues contributed to the decision to shelve
+the design for now:
+
+* lots of work went in to trying to make the board fit in a 24mm airframe,
+ but the resulting design with battery is really too heavy for such a small
+ rocket.
+
+* the 3-axis accelerometer has a max scale of +/- 6g. This is insufficient
+ for characterizing the kinds of motors that we're playing with now.
+
+* while using a gcc-based toolchain to cross-develop for the ARM7 core works
+ reasonably well, it's a heavy toolchain to build and maintain, and the
+ processor really is serious overkill for the task at hand.
+
+## Artifacts ##
+
+The best version of Bdale's [Peace Love and Rockets](AltusMetrum.odp)
+presentation about this hardware generation was given at the Ohio LinuxFest
+2008. Note that there are many photos included, so this is a HUGE file!
+
+The version 0.1 design had enough issues that Bdale decided not to publish
+it. Work on an 0.2 revision is mostly complete at the schematic level, and
+some printed circuit board artwork updates were made, but a second run of
+boards was never attempted. This design is now mostly of historical interest.
+
+## Futures ##
+
+If we decide to do further work on this design, a number of changes seem
+potentially appropriate for the next board revision, in addition to just
+fixing bugs found in the turn-on of the initial boards.
+
+* The LiPo battery support from [TeleMetrum](../TeleMetrum) should be copied
+ into this design, replacing the battery screw terminals with a standard LiPo
+ 2-pin battery connector.
+
+* The [SparkFun](http://www.sparkfun.com) folks have produced
+ a [USB bootloader for the LPC2148](http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=94). It
+ requires an SD card for temporary storage of code to be
+ flashed. Replacing the current external SPI memory chip with a microSD
+ socket could make sense. The socket size is under a cm square, and ones
+ that have a fold-up locking top are about $2, vs over $6 for the current
+ memory chip. The cards themselves are getting very cheap, too, and can
+ store much more data than the current 128k memory chip. This would require
+ moving ADC_Vbat to a different ADC input so that pins 27, 29, 30, and 31
+ would be available for the microSD socket.
+
+* Consideration should be given to changing the accelerometer for a higher-G
+ single axis unit as in [TeleMetrum](../TeleMetrum) if we want to be able to
+ use it for motor characterization.
projects / web / altusmetrum / blobdiff